Britain's Royal Air Force is flying what may be its biggest-ever peacetime rescue operation, to help people stranded by extensive flooding in central and southern England.

RAF helicopters have plucked scores of people out of the floodwaters, and rescued others clinging to the roofs of homes. Air crews also are flying in doctors and relief supplies.

Many roads and rail lines are covered by water up to two meters deep, forcing motorists and other travelers to take refuge in crowded shelters.

In Gloucestershire, in southwest England, bordering Wales, one of the counties worst affected, an estimated 150,000 residents are without drinking water, after the flood-swollen River Severn overwhelmed a water-treatment plant. The facility was shut down and evacuated, and customers are being told they will have no service for at least 72 hours.

British meteorologists say some parts of England got more than a normal month's worth of rain in just a few hours Friday. More rain is predicted for this week, but the worst-hit areas will escape most heavy precipitation.